1. Technical Field
The present invention relates to helmets for protection of a user's head in sports and other activities. More specifically, the present invention relates to customizable helmets and inserts.
2. Background Art
Helmets are designed to protect the head and brain and are used in a variety of activities and sports. Many helmets include a layer of crushable foam that crushes upon contact in order to control the crash energy and extend the stopping time of the head in order to reduce peak impact to the brain. The crushable foam is contained within a plastic skin. Often, as with bicycle helmets, once an impact has taken place, the foam does not recover to its original shape and must be replaced with a new helmet. Other types of helmets have a slow-rebound foam (butyl nitrate foam, or expanded polypropylene foam) that recover slowly after an impact and are reusable.
U.S. Pat. No. 8,528,119 to Ferrara discloses an impact-absorbing protective structure comprises one or more compressible cells that can be used in helmets. Each cell is in the form of a thin-walled plastic enclosure defining an inner, fluid-filled chamber with at least one small orifice through which fluid resistively flows. Each cell includes an initially resistive mechanism that resists collapse during an initial phase of an impact and that then yields to allow the remainder of the impact to be managed by the venting of fluid through the orifice. The initially resistive mechanism may be implemented by providing the cell with semi-vertical side walls of an appropriate thickness or by combining a resiliently collapsible ring with the cell. After the initially resistive mechanism yields to the impact, the remainder of the impact is managed by the fluid venting through the orifice. The cell properties can be readily engineered to optimize the impact-absorbing response of the cell to a wide range of impact energies. While the cells can be customized to a particular use of the helmet such as with materials of fabrication, size, geometry, etc., the helmet is not manufactured to be customized for a specific individual's head.
In physics, pressure equals force/area (P=F/A). If a person steps on a nail, it will puncture skin, whereas if a person lays on a bed of 1,000 nails, the skin is not punctured because the contact surface area is increased 1,000 fold and thus decreasing the pressure 1,000 fold. Even small changes in surface area have a dramatic decrease in pressure. For example, a sharp knife cuts through a steak very easily, whereas a dull knife requires a lot of effort to cut.
In medicine, the concept of total contact to decrease pressure of force of impact is well documented and studied. In an amputee, the weight of the body is transmitted through the bones. If one just put on an extension to weight bear the skin will break down over the area, or vectors of force, where bones transmit weight. Thus, total contact casting, created by casting with a reverse mold, and creating a total contact fit for a prosthesis is used to decrease pressure and markedly decrease any skin breakdown. Total contact casting is also used for ankle fracture immobilization, which all but eliminates heel decubitous ulcers by spreading out pressure over the area of total surface contact.
There remains a need for a helmet that can be customized to an individual's head and can more effectively reduce force of an impact.